1. Technical Field of the Invention
The invention relates to an actuating system for a hatch or similar hinged structure of a vehicle in which a powered actuating system is operative to close the hatch against a spring force tending to open the hatch.
2. The Related Art
Actuating systems of this type have an electric drive that moves a hatch or vehicle door against the force of a spring element from an open operating position towards a closed position. In daily practice, it is often desired for the hatch to assume an intermediate position and to maintain it for a relatively long period of time, especially when the vehicle is parked. In order to be able to maintain the intermediate position of the hatch for a relatively long period of time, an electrically actuatable coupling is provided as part of the actuating system. The electrically actuatable coupling, however, must be continuously supplied with power. When the engine is switched off, the electrical power supply for the coupling must perforce come from the vehicle battery. This presents the risk that, if the vehicle is parked with a vehicle hatch in an intermediate position for an excessively long period of time, the battery will be discharged to such an extent as to endanger the engine starting process.
In order to deal with this problem, the actuating system in accordance with U.S. Pat. No. 6,092,336 is provided with a freewheel device in a gearbox for a cable drive unit. When the electrically actuatable coupling is unpowered, the freewheel device prevents the hatch from opening further.
The object of the present invention is to implement an actuating system for a moving part, in particular a hatch or the like, in which an intermediate position of the hatch can be maintained in an unpowered state and a costly gearbox can be omitted.
The foregoing and other objects are attained, in accordance with the invention, by the provision of a locking device, for holding the moving part in an intermediate position, in the form of a piston/cylinder assembly which includes a flow connection between the working chambers of the cylinder and a pilot value for controllably blocking fluid flow through the fluid connection.
As a result, any gearbox that may be associated with the drive device can have a far simpler structure. Furthermore, motion of the moving part, e.g. a hatch, in both directions can be halted by the lockable piston/cylinder assembly.
In order to achieve, firstly, high retention force on the moving part and, secondly, low energy consumption for the drive device, provision is made for the pilot valve to have a two-stage opening characteristic wherein, after a relatively large unblocking force is overcome, an operating motion can be performed with a smaller hold-open force.
In a relatively simple control version of the system, the threshold value is shifted independently of an intermediate position of the moving part such that the unblocking force is overcome by the drive device.
In a somewhat more complex solution, the control system has at least two threshold values, wherein one threshold value for an obstacle is overcome during motion of the moving part and a second threshold value is overcome by the drive device when the moving part is set into motion from a stop. In this way, a finer obstacle detection response is achieved for the moving part.
In an alternative solution, the pilot valve has an electric actuator that is disconnected from the power supply of a generator of a vehicle and moved to a locking position when the vehicle engine is stopped. As soon as the vehicle engine stops, locking is achieved in the unpowered state. During vehicle operation, a sufficient supply of power is available to continuously hold the pilot valve open if this is necessary.
For the situation where it is desired to actuate the pilot valve when the engine is stopped as well, power supply from a battery can be connected to the power supply of the generator.